Symetrix 601 User manual

S
y
metrix Inc.
14926 35th Avenue West
L
y
nnwood, Washin
g
ton 98036
voice:
(
206
)
787-3222
(
800
)
288-8855
fax:
(
206
)
787-3211
Owner’s Manual
Manual: Rev 2.2, 10/31/94
Software: Rev 2.03
Part number: 530204
Subject to change at our whim, and without notice.
Copyright (c) 1992-1994, Symetrix Inc. All rights reserved.
Batteries not included. Ground isn’t ground!
Available at finer studios everywhere.
No part of this manual may be reproduced or transmitted in any form or by any
means, electronic or mechanical, including photocopying, recording or by any
information storage and retrieval system, without permission, in writing, from
the publisher.
Symetrix
601601
Digital Voice ProcessorDigital Voice Processor

Production Information
This document was written using Microsoft Word for Windows V2.0 and 6.0. The drawings and graphs in
this manual were prepared using Corel Draw V2.0, Autocad V12, and Autoscript V5, then imported into
Word for Windows via encapsulated PostScript files. All page makeup occurred within Word for Windows.
Body text is set in Bookman 10pt and Section Heads are set in various sizes of Helvetica Bold. Helvetica-
Narrow was used for Figure and Table captions.
This manual was printed directly from PostScript files generated by Word for Windows on a Xerox
Docutech printer. This unique device is actually a laser printer, capable of 600 dpi resolution, with a
page throughput that rivals a high-speed photocopier. As a result, every page is a first-generation image.
Ain’t technology grand?

i
Table of Contents
1. Introduction ............................................................................................1-1
1.1 Manual Sections ..............................................................................................1-2
1.2 Operator Safety Summary ...............................................................................1-2
1.2.1 Equipment Markings .....................................................................................1-3
1.2.2 Terms............................................................................................................1-3
1.3 Other Safety Information..................................................................................1-4
2. Basics......................................................................................................2-1
2.1 What Does the 601 Do?...................................................................................2-1
2.2 Digital and Analog Differences.........................................................................2-1
2.3 Gain Setting.....................................................................................................2-1
2.4 Equalization .....................................................................................................2-2
2.4.1 Power and Fullness.......................................................................................2-2
2.4.2 Rhythm and Musical Foundation...................................................................2-2
2.4.3 Telephone Quality.........................................................................................2-3
2.4.4 Lisping Quality ..............................................................................................2-3
2.4.5 Presence Range...........................................................................................2-3
2.4.6 Brilliance .......................................................................................................2-3
2.4.7 Conclusions ..................................................................................................2-4
2.4.8 Equalizing for Speech...................................................................................2-4
2.4.9 Peaking or Shelving?....................................................................................2-6
2.5 De-Essing........................................................................................................2-6
2.6 Noise Reduction...............................................................................................2-7
2.7 Downward Expansion ......................................................................................2-7
2.8 Compression....................................................................................................2-7
2.9 AGC.................................................................................................................2-8
2.10 Delay..............................................................................................................2-9
2.11 Modulated Delay............................................................................................2-9
2.12 MIDI...............................................................................................................2-9
2.13 Program Memory...........................................................................................2-10
3. Technical Tutorial ..................................................................................3-1
3.1 Matching Levels vs Matching Impedances.......................................................3-1
3.2 Signal Levels....................................................................................................3-2
3.3 I/O Impedances ...............................................................................................3-2
3.4 Polarity Convention..........................................................................................3-3
3.5 Input and Output Connections .........................................................................3-3
3.6 Digital I/O Considerations ................................................................................3-5
3.7 MIDI I/O Considerations...................................................................................3-5
3.8 3-5
3.9 Phantom Powering Condenser Microphones...................................................3-5
4. Front Panel Overview ............................................................................4-1
4.1 User Interface Summary..................................................................................4-1

ii
4.1.1 Loading Programs.........................................................................................4-1
4.1.2 Saving Programs ..........................................................................................4-1
4.1.3 Comparing Programs....................................................................................4-2
4.2 Rate of Change Parameter..............................................................................4-2
4.3 Input Level Control Block.................................................................................4-2
4.4 Parametric EQ Block........................................................................................4-3
4.4.1 EQ Band Select ............................................................................................4-3
4.4.2 EQ Parameter Group....................................................................................4-4
4.5 Dynamics Processing Block.............................................................................4-4
4.5.1 Dynamic Noise Reduction Block ...................................................................4-4
4.5.2 De-Esser Block.............................................................................................4-5
4.5.3 Downward Expander Block...........................................................................4-6
4.5.4 Compressor Parameter Block.......................................................................4-7
4.5.5 AGC Block ....................................................................................................4-7
4.5.6 Dynamics Section Control Summary.............................................................4-9
4.5.7 Additional Dynamics Parameters ..................................................................4-9
4.5.7.1 Sidechain filter ...........................................................................................4-10
4.5.7.2 Expander knee control...............................................................................4-11
4.5.7.3 Compressor knee control...........................................................................4-11
4.5.7.4 AGC absolute threshold.............................................................................4-11
4.5.7.5 AGC knee control.......................................................................................4-11
4.5.7.6 ARM peak release TC................................................................................4-11
4.5.7.7 ARM integration TC....................................................................................4-11
4.5.7.8 ARM Signal/Noise threshold ......................................................................4-11
4.5.7.9 Log converter time constant.......................................................................4-11
4.5.7.10 Lookahead delay time..............................................................................4-11
4.5.7.11 De-ess absolute threshold........................................................................4-12
4.6 Delay Group.....................................................................................................4-12
4.7 Output Group...................................................................................................4-14
4.8 System Group..................................................................................................4-14
4.8.1 Global Switch................................................................................................4-14
4.8.2 MIDI Switch...................................................................................................4-15
4.9 Presets Group..................................................................................................4-16
4.10 Setting Scenarios...........................................................................................4-17
4.11 Restoring Factory Presets..............................................................................4-19
4.12 Disabling the Front Panel...............................................................................4-19
5. Rear Panel Overview..............................................................................5-1
6. Fast First Time Setup.............................................................................6-1
6.1 Connections.....................................................................................................6-1
6.2 Settings for Analog Sources.............................................................................6-2
6.3 Settings for Digital Sources..............................................................................6-4
7. Using the 601..........................................................................................7-1
7.1 Installation........................................................................................................7-1
7.2 Operational Details ..........................................................................................7-1
7.2.1 Stand-alone Operation..................................................................................7-2
7.3 Block Diagrams................................................................................................7-4
7.3.1 Overall Block Diagram ..................................................................................7-4
7.3.2 Sequence of Processing...............................................................................7-4
7.3.3 Dynamics Block ............................................................................................7-4
7.3.4 De-Ess and Noise Reduction Block...............................................................7-5
7.3.5 Delay Block...................................................................................................7-5
7.4 System Interface..............................................................................................7-6
7.4.1 Using the 601 as a Channel Insert Device ....................................................7-6

iii
7.4.2 Using the 601 in a Send-Receive Loop.........................................................7-6
7.4.3 Using the 601 as an A-D Converter ..............................................................7-6
7.4.4 External Sample-Rate Clock.........................................................................7-6
7.4.5 Input/Output/Clock Summary........................................................................7-7
7.4.6 MIDI Programming........................................................................................7-7
7.4.7 Accessing Parameters via MIDI....................................................................7-8
7.4.8 Realtime MIDI...............................................................................................7-8
7.4.9 Program Storage...........................................................................................7-8
7.4.10 Editing Parameters not Accessible from the Front Panel ............................7-9
7.5 Tips and Techniques for Using the 601............................................................7-10
7.5.1 Recalling and Storing Settings......................................................................7-10
7.5.2 Metering........................................................................................................7-10
7.5.3 Gain Setting..................................................................................................7-11
7.5.4 Equalization ..................................................................................................7-11
7.5.5 Metering and the Dynamics Block.................................................................7-12
7.5.6 Dynamic Noise Reduction.............................................................................7-12
7.5.7 De-Esser.......................................................................................................7-12
7.5.8 Compression.................................................................................................7-13
7.5.9 AGC 7-13
7.5.10 Downward Expander...................................................................................7-13
7.5.11 Delay...........................................................................................................7-14
7.5.11.1 Echo effects.............................................................................................7-14
7.5.11.2 Flanging...................................................................................................7-14
7.5.11.3 Chorus effects..........................................................................................7-15
8. Applications............................................................................................8-1
8.1 Broadcast Voice Processing ............................................................................8-1
8.2 Voice-over Processing.....................................................................................8-1
8.3 Foley Processing .............................................................................................8-1
8.4 Digital Mastering..............................................................................................8-1
8.5 Musical Applications.........................................................................................8-1
8.6 Sound Reinforcement Applications ..................................................................8-1
9. Troubleshooting Chart...........................................................................9-1
10. 601 Digital Voice Processor Limited Warranty..................................10-1
11. Repair Information ...............................................................................11-1
11.1 Return Authorization ......................................................................................11-1
11.2 In-Warranty Repairs.......................................................................................11-1
11.3 Out-of-Warranty Repairs................................................................................11-1
12. Specifications.......................................................................................12-1
A. Editing Realtime Midi Settings.............................................................A-1
A.1 Realtime MIDI Example...................................................................................A-2
B. Using the Lexicon MRC to Edit Realtime MIDI Settings.....................B-1
C. MIDI Implementation Notes...................................................................C-1
C.1 C-1
C.1 Overview.........................................................................................................C-1
C.1.1 Control Change (B
n ).....................................................................................C-1
C.1.1.1 Example ....................................................................................................C-1
C.1.2 Realtime MIDI...............................................................................................C-1
C.1.3 Sysex Implementation (F0)...........................................................................C-2

iv
C.1.4 Sysex Echo ..................................................................................................C-3
C.1.5 Recognized MIDI Commands.......................................................................C-4
C.1.6 Data Structure Per Program.........................................................................C-8
C.1.7 MIDI Parameter Tables ................................................................................C-14
C.2 Hexadecimal Conversion Tables.....................................................................C-22
D. Glossary and Bibliography...................................................................D-1
D.1 Glossary..........................................................................................................D-1
D.2 Bibliography.....................................................................................................D-11
E. Architect’s and Engineer’s Specification............................................E-1
F. Disassembly Instructions......................................................................F-1
F.1 Top Cover Removal.........................................................................................F-1
F.2 Circuit Board Removal.....................................................................................F-1
F.2.1 Analog Board Removal.................................................................................F-1
F.2.2 Digital Board Removal..................................................................................F-2
F.2.3 Power Supply Board Removal......................................................................F-2
F.2.4 Front Panel Board Removal..........................................................................F-2
F.3 XLR Connector Removal (Important!!).............................................................F-2
G. Presets and Other Stuff ........................................................................G-1
G.3 Presets and Building Blocks............................................................................G-4

v
List of Tables
TABLE 1. EDIT BUFFER DATA REQUEST ...................................................................................................... C-4
TABLE 2. EDIT BUFFER DATA RESPONSE .................................................................................................... C-4
TABLE 3. EDIT BUFFER DATA SET............................................................................................................... C-4
TABLE 4. PROGRAM/SETUP DATA REQUEST................................................................................................ C-5
TABLE 5. DATA RESPONSE......................................................................................................................... C-5
TABLE 6. PROGRAM/SETUP DATA WRITE .................................................................................................... C-6
TABLE 7. IDENTIFY REQUEST...................................................................................................................... C-6
TABLE 8. IDENTIFY RESPONSE.................................................................................................................... C-6
TABLE 9. PARAMETER MAP......................................................................................................................... C-7
TABLE 10. GLOBAL..................................................................................................................................... C-8
TABLE 11. FILTER 1.................................................................................................................................... C-8
TABLE 12. FILTER 2.................................................................................................................................... C-8
TABLE 13. FILTER 3.................................................................................................................................... C-8
TABLE 14. DE-ESS PROCESSOR ................................................................................................................. C-9
TABLE 15. NOISE REDUCTION PROCESSOR................................................................................................. C-9
TABLE 16. DELAY PROCESSOR................................................................................................................... C-9
TABLE 17. EXPANSION PARAMETERS........................................................................................................ C-10
TABLE 18. COMPRESSION PARAMETERS................................................................................................... C-10
TABLE 19. AGC PARAMETERS.................................................................................................................. C-10
TABLE 20. ARM SENSE PARAMETERS ...................................................................................................... C-11
TABLE 21. LOG CONVERTER PARAMETERS.............................................................................................. C-11
TABLE 22. OUTPUT .................................................................................................................................. C-11
TABLE 23. REALTIME MIDI BLOCK 1......................................................................................................... C-12
TABLE 24. REALTIME MIDI BLOCK 2......................................................................................................... C-13
TABLE 25. MISCELLANEOUS...................................................................................................................... C-13
TABLE 26. ATTN18 TABLE (DB) ................................................................................................................ C-14
TABLE 27. ATTN82 TABLE (DB) ................................................................................................................ C-14
TABLE 28. ATTN100 TABLE (DB) .............................................................................................................. C-14
TABLE 29. PARAMETRIC BANDWIDTH TABLE (IN OCTAVES)......................................................................... C-15
TABLE 30. FREQUENCY TABLE (HZ).......................................................................................................... C-15
TABLE 31. OUTPUT LEVEL TABLE (DB)...................................................................................................... C-15
TABLE 32. EXPANDER RATIO TABLE.......................................................................................................... C-16
TABLE 33. COMPRESSOR RATIO TABLE..................................................................................................... C-16
TABLE 34. AGC RATIO TABLE .................................................................................................................. C-16
TABLE 35. ARM THRESHOLD (DB)............................................................................................................ C-17
TABLE 36. TIME CONSTANT TABLE............................................................................................................ C-17
TABLE 37. COMPRESSER/EXPANDER KNEE TABLE (IN DB): ........................................................................ C-17
TABLE 38. MAKEUP GAIN TABLE (ATTN24)................................................................................................ C-18
TABLE 39. SIDECHAIN LOOKAHEAD TIME (MS) TABLE................................................................................. C-18
TABLE 40. DELAY TIME TABLE (MS) .......................................................................................................... C-18
TABLE 41. DELAY FEEDBACK TABLE: NEGATIVE THEN POSITIVE FEEDBACK (DB)........................................ C-19
TABLE 42. DELAY LINE FILTER TABLE ....................................................................................................... C-19
TABLE 43. REALTIME SCALING TABLE ....................................................................................................... C-19
TABLE 44. DEFAULT PAN TABLE ............................................................................................................... C-20
TABLE 45. NORMALIZED MIDI PAN INPUT TABLE ....................................................................................... C-21
TABLE 46. HEX TO DECIMAL ..................................................................................................................... C-22
TABLE 47. DECIMAL TO HEX ..................................................................................................................... C-22

vi
Alphabetical List of Tables
AGC PARAMETERS TABLE 19. C-10
AGC RATIO TABLE TABLE 34. C-16
ARM SENSE PARAMETERS TABLE 20. C-11
ARM THRESHOLD (DB) TABLE 35. C-17
ATTN100 TABLE(DB) TABLE 28. C-14
ATTN18 TABLE(DB) TABLE 26. C-14
ATTN82 TABLE(DB) TABLE 27. C-14
COMPRESSER/EXPANDER KNEE TABLE(IN DB): TABLE 37. C-17
COMPRESSION PARAMETERS TABLE 18. C-10
COMPRESSOR RATIO TABLE TABLE 33. C-16
DATA RESPONSE TABLE 5. C-5
DE-ESS PROCESSOR TABLE 14. C-9
DECIMAL TO HEX TABLE 47. C-22
DEFAULT PAN TABLE TABLE 44. C-20
DELAY FEEDBACK TABLE: NEGATIVE THEN POSITIVE FEEDBACK (DB) TABLE 41. C-19
DELAY LINE FILTER TABLE TABLE 42. C-19
DELAY PROCESSOR TABLE 16. C-9
DELAY TIME TABLE(MS) TABLE 40. C-18
EDIT BUFFER DATA REQUEST TABLE 1. C-4
EDIT BUFFER DATA RESPONSE TABLE 2. C-4
EDIT BUFFER DATA SET TABLE 3. C-4
EXPANDER RATIO TABLE TABLE 32. C-16
EXPANSION PARAMETERS TABLE 17. C-10
FILTER 1 TABLE 11. C-8
FILTER 2 TABLE 12. C-8
FILTER 3 TABLE 13. C-8
FREQUENCY TABLE (HZ) TABLE 30. C-15
GLOBAL TABLE 10. C-8
HEX TO DECIMAL TABLE 46. C-22
IDENTIFY REQUEST TABLE 7. C-6
IDENTIFY RESPONSE TABLE 8. C-6
LOG CONVERTER PARAMETERS TABLE 21. C-11
MAKEUP GAIN TABLE (ATTN24) TABLE 38. C-18
MISCELLANEOUS TABLE 25. C-13
NOISE REDUCTION PROCESSOR TABLE 15. C-9
NORMALIZED MIDI PAN INPUT TABLE TABLE 45. C-21
OUTPUT TABLE 22. C-11
OUTPUT LEVEL TABLE (DB) TABLE 31. C-15
PARAMETER MAP TABLE 9. C-7
PARAMETRIC BANDWIDTH TABLE (IN OCTAVES) TABLE 29. C-15
PROGRAM/SETUP DATA REQUEST TABLE 4. C-5
PROGRAM/SETUP DATA WRITE TABLE 6. C-6
REALTIME MIDI BLOCK 1 TABLE 23. C-12
REALTIME MIDI BLOCK 2 TABLE 24. C-13
REALTIME SCALING TABLE TABLE 43. C-19
SIDECHAIN LOOKAHEAD TIME (MS) TABLE TABLE 39. C-18
TIME CONSTANT TABLE TABLE 36. C-17

1-1
Rev 2.2, 10/31/94
-4 -2
3 2 CLIP
-9 -6-20 -12
618 12 4
-24
24
PRESETS
SAVE COMPARE
LOAD EDIT
LEAVE
SYSTEM
GLOBALBYPASS
OUTPUT
MIDIDEPTH PAN
GAIN(dB) /
GAIN REDUCTION (dB)
OUTPUT HEADROOM (dB)
DELAY
DELAY(mS)MIX
RATEFILTER
ATTACK(mS)
DYNAMICS PROCESSING
COMPRESS
RATIO(X:1)AGC FREQ(kHz) / THRESH(dB)
RELEASE(mS)
DS
LEVEL(dB)
NR
BAND 3
BP
BAND 2
BP
PARAMETRIC EQ
HIGH WIDTH(Oct)
FREQ(kHz)
EXPANDER
CLIP4312 6 2
+4-1050
LINE
24 1848 36
0
IN / SYNC
DIGITAL
MIC
INPUT HEADROOM (dB)
INPUT LEVEL CONTROL
LOW
BAND 1
BP FEEDBACK
MODULATION
1. Introduction
The Symetrix 601 Digital Voice Processor is a single-channel digital voice processor intended for
use in a variety of recording, broadcast, live sound and post production applications. Acting as
a "bridge" between the analog and digital domains, the 601 accepts microphone or line level
analog signals, converts them to 18-bit digital (44.1 kHz or 48 kHz sample rates), performs 24-
bit digital signal processing, and sends them on their way via the digital and analog outputs.
The 601 uses two Motorola DSP-56001 digital signal processors (DSP) for an overall processing
rate of 40 million instructions per second (40 MIPS).
The 601 has inputs and outputs accommodating all common analog and digital formats. The
following table lists all of the inputs and outputs.
Input Mode Output Mode
Microphone A Line (x2) A
Line A
AES/EBU D AES/EBU D
S/PDIF D S/PDIF D
The microphone and line inputs may be used individually or mixed. The input and output
modes are separate; you can use almost any combination of the analog and digital outputs
simultaneously (for example, the AES/EBU and S/PDIF digital outputs cannot be used
simultaneously).
While the 601 works great for voice (singing or monologue/dialogue) enhancement, its powerful
digital engine works wonders on any signal. Processing includes fully parametric EQ, shelving
EQ, notch filtering, dynamic noise filtering, de-essing, delay (first reflection), stereo synthesis,
gating, expansion, compression, and AGC (automatic gain control). Get the picture?
One aspect of many digital processors is the difficulty of use. The 601 was designed to be easy
to use, yet powerful. There are no menus to scroll through. Each parameter is visible via the
front panel push-switches. Pressing a switch transfers the display to that parameter's current
value. The parameter wheel allows you to change the value. Finally, the 601 allows you to
compare your stored setting with the current (edited) setting, without committing the edited
settings to memory.
Of course, all this processing power can be remotely controlled via MIDI. The 601's MIDI
implementation includes simple program change as well as parameter editing.
All analog inputs and outputs are available via XLR connectors. The AES/EBU digital inputs
and outputs use XLR connectors and the S/PDIF digital inputs and outputs use RCA
connectors. The MIDI input and output connections use standard 5-pin female DIN connectors.
The 601's unique set of digital tools can make voices, instruments, or sound effects jump out of
any mix.; Its combination of factory presets and non-volatile user program space guarantee
predictable and repeatable effects from session to session, performance to performance.
We recommend that you read this manual from cover to cover. Somewhere between the
confines of the two covers you should find the answers to most (98%) of your questions, both
technical as well as musical.
If you're in a hurry (like most of us), or if you really don't believe that someone could write a
decent owners manual that you can read and understand, then do us both a favor and read the

1-2 Rev 2.2, 10/31/94
remainder of this section and Chapter 6, "Fast First Time Setup." Chapter 6 will help you get
connected, tell you what the knobs do, and send you on your way. For MIDI information, go
directly to Appendix C, which describes some of the things that you can do with the 601 using
MIDI.
1.1 Manual Sections
This manual contains the following sections:
Chapter 1. Introduction introduces the 601 and this manual. Describes important safety
information
Chapter 2. Basics lets you know what the 601 does, and how it does it and some basic usage
information..
Chapter 3. Technical Tutorial a basic and not-so-basic discussion of signal levels, input and
output impedances, and connection polarity.
Chapter 4. Front Panel Overview gives a brief look at the controls and switches located on the
front panel of the 601.
Chapter 5. Rear Panel Overview gives a brief look at the rear panel of the 601.
Chapter 6. Fast, First Time Setup is a section written especially for people who just can't wait to
get their hands on the knobs.
Chapter 7. Using the 601 describes the use of the 601 in detail.
Chapter 8. Applications describes some of the myriad uses for the 601.
Chapter 9. Troubleshooting tells what to do if the 601 doesn't work.
Chapter 10. Limited Warranty describes the 601's warranty.
Chapter 11. Repair Information tells how to get your 601 repaired.
Chapter 12. Specifications lists the technical specifications of the 601's performance.
Appendix A. Appendix A describes how to use the realtime MIDI features built into the 601.
Appendix B. Appendix B tells how to use the Lexicon MRC with the 601.
Appendix C. Appendix C describes how to communicate with the 601 via MIDI. This appendix
also contains a description of the 601's Midi implementation.
Appendix D. Appendix D contains a glossary and a useful bibliography.
Appendix E. Appendix E contains the Architects and Engineer's specifications.
Appendix F. Appendix F contains disassembly instructions.
Appendix G. Appendix G contains a listing of the preset programs and other miscellany.
1.2 Operator Safety Summary
The information in this summary is intended for persons who operate the equipment as well as
repair personnel. Specific warnings and cautions are found throughout this manual wherever
they may apply; they do not appear in this summary.

1-3
Rev 2.2, 10/31/94
The notational conventions used in this manual and on the equipment itself are described in
the following paragraphs.
The lightning flash with arrowhead symbol
within an equilateral triangle is intended to
alert the user of the presence of uninsulated
"dangerous voltage" within the product's
enclosure that may be of sufficient
magnitude to constitute a risk of electric
shock to
p
ersons.
The exclamation point within an equilateral
triangle is intended to alert the user of the
presence of important operating and
maintenance (servicing) instructions in the
literature accompanying the appliance (i.e.
this manual).
Caution
To prevent electric shock, do not use the polarized plug supplied with this appliance with
any extension cord, receptacle, or other outlet unless the blades can be fully inserted to
prevent blade exposure.
1.2.2 Terms
Several notational conventions are used in this manual. Some paragraphs may use Note,
Caution, or Warning as a heading. These headings have the following meaning:
Convention Description
Caution Identifies information that, if not heeded, may cause
damage to the 601 or other equipment in your system.
Note Identifies information that needs extra emphasis. A Note
generally supplies extra information to help you use the
601 better.
Warning Identifies information that, if ignored, may be
hazardous to your health or that of others.
In addition, certain typefaces and capitalization are used to identify certain words. These
situations are:
Convention Meaning
CAPITALS Controls, switches or other markings on the chassis.
Boldface Strong emphasis.
Helvetica-Narrow
Information appearing on the LED display
1.2.1 Equipment Markings
S’adresser a un reparateur compétent.
Il ne se trouve a l’interieur aucune piece pourvant entre reparée l’usager.
No user serviceable parts inside. Refer servicing to qualified service personnel.
NE PAS OUVRIR
RISQUE DE CHOC ELECTRIQUE
ATTENTION:
CAUTION
DO NOT OPEN
RISK OF ELECTRIC SHOCK

1-4 Rev 2.2, 10/31/94
Finally, two symbols are used as visual hints. They are:
Symbol Meaning
NHelping hand. A hint to make your life a bit easier.
MThe Bomb. A visual way of saying, “Caution!”
1.3 Other Safety Information
Power Source This product is intended to operate from a power source
that does not apply more than 250V rms between the
power supply conductors or between either power
supply conductor and ground. A protective ground
connection, by way of the grounding conductor in the
power cord, is essential for safe operation
Grounding The chassis of this product is grounded through the
grounding conductor of the power cord. To avoid electric
shock, plug the power cord into a properly wired
receptacle before making any connections to the
product. A protective ground connection, by way of the
grounding conductor in the power cord, is essential for
safe operation.
Danger from Loss of
Ground
If the protective ground connection is lost, all accessible
conductive parts, including knobs and controls that may
appear to be insulated, can render an electric shock.
Proper Power Cord Use only the power cord and connector specified for the
product and your operating locale.
Use only a cord that is in good condition.
Proper Fuse The fuse is mounted internally and is not considered
user serviceable. The fuseholder accepts American sized
fuses (1/4 in. dia.) or European sized fuses (5 mm dia).
For 117V ac operation, the correct value is 1/2A, 250V
ac, fast blowing (Bussman type AGC).
For 230V ac operation, the correct value is 1/4A, 250V
ac, slow blowing (Bussman type MDL or GDC) .
Operating Location Do not operate this equipment under any of the
following conditions: explosive atmospheres, in wet
locations, in inclement weather, improper or unknown
AC mains voltage, or if improperly fused.
Stay Out of the Box To avoid personal injury (or worse), do not remove the
product covers or panels. Do not operate the product
without the covers and panels properly installed.
User-serviceable parts There are no user serviceable parts inside the 601. In
case of failure, refer all servicing to the factory. The
complexity of the DSP circuitry as well as the special
assembly tools required make the feasibility of field
service doubtful.

2-1
Rev 2.2, 10/31/94
2. Basics
If the particular combination of processors in the 601 is strange or foreign to you, then we
suggest that you read and digest this section of the manual. If you should find some of the
terminology strange, you'll find a glossary of terms at the end of the manual. A very good
dictionary-style reference is also listed in the Bibliography.
2.1 What Does the 601 Do?
The 601 is a unique combination of four digital signal processors in one box: a versatile three-
band parametric equalizer, a dynamic filter, a dynamics processor, and a digital delay. All of
these processors are implemented in the digital domain and the 601 can accept (or output)
signals in either the analog or digital domains.
One way to think about the particular combination of processors in the 601 is in terms of a
modern mixing console. Today, most mixing consoles have microphone and line inputs, some
sort of equalization, effects sends and returns, and (occasionally) on-board dynamics
processing. For a typical voice-over session, you would probably have a compressor/limiter and
a digital delay patched in as outboard processors. The 601 provides each of these processors
wrapped into one tidy one rack-space package.
2.2 Digital and Analog Differences
A large difference between the 601 and a mixing console is that the processing functions in the
601 are implemented totally within the digital domain whereas those within the console are
most likely implemented in the analog domain.
Outwardly there is no difference between an analog and a digital processor. A digital parametric
equalizer has the same controls that you're familiar with in the analog world. Granted, the way
that you access these controls may be different, but how much difference is there in seeing +9
dB on an LED display or in reading it off of a knob against a scale on the front panel?
2.3 Gain Setting
Wire is probably the only component of a sound system where we don't need to take signal
levels into account (usually). Any other active component of a sound system that passes signal
has a finite dynamic range. This means that our old friends dynamic range, headroom, and
noise floor are present and must be accounted for.
Tackling these terms in reverse order, noise floor represents the signal level of the device's
residual noise level. Realistically, this is somewhat lower than the lowest signal level that you'd
want to process (unless you want the output to sound noisy).
Headroom is the difference between the average signal level and peak clipping. Peak clipping
occurs because the processor can't increase its output to follow the signal. When this occurs,
the output signal simply flat-tops over the period that it can't follow its input (sort of like
clipping the tip of the peak off with a hedge-trimmer to level it off). Audibly speaking, clipping
and using the hedge-trimmer are about equivalent.
Dynamic range is the difference between the highest signal that may pass (limited by peak
clipping) and the lowest signal that will pass (limited by the noise floor). In a digital processor, a
0 dB signal may output a -120 dB noise floor but the smallest signal that may be represented
by 18-bits is a -108 dB square wave (because there is only one bit to toggle on and off).
Somewhere between these two points is the average level of your signal, as set by the
processor's level control. Set the average level too high and peak clipping will smash your peaks
flat, set it too low and suddenly the noise floor becomes audible (but you've got lots of
headroom!).

2-2 Rev 2.2, 10/31/94
The 601 allows you to set the signal levels in three different locations, which allows you to
make the best tradeoff between headroom and dynamic range. The analog inputs each have
gain controls to help you run these stages as hot as possible, without clipping. After conversion
to digital form, some signals may be too hot for any signal processing that results in an
increasing signal level. Thus, the 601 has a digital gain control that allows you to raise or lower
the level sent to the digital processors. Finally, there is an overall digital output gain control
allowing you to restore the signal level to "normal."
2.4 Equalization
Equalization is nothing more than selectively (or not) amplifying a signal based on frequency.
Since audio signals consist of combinations of fundamental signals and their harmonics,
changing the tonality or the spectral balance of a signal involves nothing more than altering the
relationship of the fundamental to its harmonics, and of the harmonics to themselves. Each
harmonic is responsible for one aspect of the audible character of a signal; knowing these
relationships allow you to quickly zero-in on the correct frequency range of the signal and
quickly apply boost or cut to enhance or correct what you are hearing.
The audio spectrum has several critical portions that are responsible for our perceptions of
sounds that we hear:
1
2.4.1 Power and Fullness.
In the very low bass region lies the threshold of feeling, where the lowest sounds, like wind, room
effects, and distant thunder, are felt, rather than heard. In the upper half of the first octave of
this range, research has shown that the fundamentals of piano, organ and even the harp reach
well into this range. Harvey Fletcher (of Fletcher-Munson fame) charted the sensitivity of the ear
for various parts of the spectrum at levels that are lower than those of reality. Fletcher's
compensation curves (the well known Fletcher-Munson curves) show that for equal loudness in
this range at lower recorded and reproduced levels shows requirements for tremendous boosts,
on the order of 10 to 30 dB. Aside from the subjective effects of this range, the ability to control
unwanted sounds in this range is equally important to subdue stage rumble and outside traffic
noise (especially important where there are subways beneath buildings!). Overemphasis caused
by close cardioid microphone placement can cause muddiness in the overall sound;
attenuating (cutting) the very-low-bass region can greatly improve overall clarity.
2.4.2 Rhythm and Musical Foundation.
In the bass region, most of the low, grave tones of the drum and piano can be found. Here we
can also find the fundamentals of the rhythm section, as well as the foundation of all musical
structure.
It was Leopold Stowkowski who said "If I had a thousand bass viols I could use them all!" This is not
as extreme as it may sound. A bass viol, even though it is reinforced by its sounding board,
generally plays single notes and possesses little dynamic range. In a large orchestra, as many as
1The majority of the material in section 2.4 is taken from "Equalizing for Spectral
Character," Langevin Corporation, 1966 Catalog.
Range Frequencies Musical Location
Very Low Bass 16-64 Hz 1st and 2nd octaves.
Bass 64-256 Hz 3rd and 4th octaves.
Midrange 256-2048 Hz 5th, 6th, and 7th octaves.
Lisping Quality 3000 Hz Between the 7th and 8th octaves.
Presence Range 4750-5000 Hz Between the 8th and 9th octaves.
Brilliance 6500-16 kHz Part of the 9th through the 10th octave.

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Rev 2.2, 10/31/94
eight bass viols may be used. A total of 1000 bass viols in this case would only give an additional
21 dB of level, which is not an inordinate amount given a glance at Mr. Fletcher's equal loudness
curves. Pay attention to this range because the overall musical balance of your program can be
controlled by equalizing or attenuating the 100 Hz range.
2.4.3 Telephone Quality
The ear is reasonably sensitive in the midrange frequencies, and sound restricted to this range
has a telephone-like quality (which is generally why telephone-quality frequency response
covers the 300-3 kHz range).
If you make the 6th octave (500-1024 Hz) louder with respect to the other octaves, the
subjective result is a horn-like quality. If you emphasize the 7th octave (1000-2000 Hz), the effect is
one of tinniness.
The fundamental tones in most music lie equally above and below middle C (261 Hz), from 128 to
512 Hz. As most instruments are rich in the first overtones, the majority of sound energy is found up
to the 2.5 kHz range. Music editors and others engaged in listening to music over long periods
find that listening fatigue can be reduced by attenuating the 5th, 6th, and 7th octaves by about
5 dB.
2.4.4 Lisping Quality
The 3 kHz range delivers a generous stimulus to the ear. At very loud levels the region of greatest
ear sensitivity shifts downward from 5 kHz; this is why many "PA" speakers have broad peaks in this
region. A characteristic of low-level signals peaked at 3 kHz is a "lisping" quality, and the total
inability to distinguish labial sounds such as m, b, and v.
In wide-range lower level systems, a peak in the 3 kHz region has a masking effect on important
recognition sounds, and on others which lie above 4 kHz. Brilliance and clarity are lost and
without attenuation of this region, an unconscious strain with increasing fatigue is felt according
to the amount of 3 kHz boost.
2.4.5 Presence Range
The usual band affecting clarity in male speech is 3000 to 6000 Hz. In a woman's voice, the
fundamentals are roughly an octave higher than a man's, and a woman's range of consonant
clarity lies between 5000 and 8000 Hz (the high-end of this range approaches a region of
hearing insensitivity in humans). Furthermore, the total range of a woman's voice is about half
that of a mans, stimulating fewer hearing nerves, and for this reason, is consequently still weaker
upon reception.
Wide range sounds, especially those of singing voices, have fundamentals with harmonics in the
5 kHz region of good ear sensitivity. Voices that are powerful or rich with harmonics at 5 kHz
sound especially pleasing, clear and full. Male opera singers are particularly favored with 5 kHz
sounds, women less so. In popular music, this range shifts downward somewhat. It follows that
voices deficient in the 5 kHz range can be enhanced in listening value by a generous boost on
the order of 5 to 8 dB at 5 kHz. A secondary benefit of this boost is an apparent increase in level;
a 6 dB rise at 5 kHz frequently gives an apparent increase of 3 dB to the overall signal.
Attenuating the 5 kHz range on instruments gives a "transparent" quality to the sound, providing,
of course, that the remainder of the signal is otherwise wide range. Microphones having a dip in
this region lack the "punch" or "presence" to which we (Americans) are accustomed.
2.4.6 Brilliance
Unvoiced consonants attributed to tooth, tongue and lip sounds are high in frequency, and
reach the 10 kHz range. These frequencies account for some clarity and most brilliance, even
though they contain less than 2% of the total speech energy. This also holds true for musical
instruments; especially percussion. Boosting or cutting this range affects clarity and naturalness.

2-4 Rev 2.2, 10/31/94
In speech, the 9th and 10th octaves impart intimacy although too much emphasis can make
secondary speech sounds (lip smacking, etc.) objectionable (a good case for a downward
expander).
Some microphones having a rise at the higher frequencies (especially omni microphones)
benefit from some attenuation in this region. Those microphones having underdamped
diaphragms may ring at these frequencies, causing an annoying sibilant distortion on speech.
On musical forms using hand percussion, boosting this range frequently results in an astonishing
and pleasing feeling of clarity.
2.4.7 Conclusions
When the article containing the above excerpts was written (probably around 1963), stereo was
just becoming a commercial reality (you could still purchase mono and stereo versions of an LP
and there were still more FM stations broadcasting in mono than stereo), and as many mixers
contained rotary mix pots as those that used slide pots. The value of individual channel
equalization was known, but it was both technologically and financially prohibitive. The article
concludes thusly:
"With the advent of stereo and three-channel recording, nearly three times the
equipment, with more elaboration, seems indicated, and expansion of console area in
the horizontal plane offers the only direction in which to proceed. But a single engineer
has arms only so long."
How times have changed!
2.4.8 Equalizing for Speech
In broadcast, equalizers are often used to create a sonic personality for the station's on-air
personalities. In the past, this has often meant using a single non-programmable equalizer in
the announce mic's signal chain. Considering the inverse rule of the knobs (the more knobs
you give them, the easier it is for someone to get hopelessly screwed up!), the attitude of most
station's PDs and engineers was to hide the equalizer somewhere, preferably under lock and
key. The 601makes it easy for each personality to have their own, individualized, curve.
Granted, if you give the jocks access to the unit, someone will inevitably shoot themselves in
the foot, but at least everyone can have their own curve.
Some general thoughts on speech equalization:
1. Try to use wider bandwidths. Narrower bandwidths (1/2 octave and less) are less audible
(harder to hear) and are generally only useful for remedial work. Broader bandwidths are
less obnoxious, more pleasing sounding, and easier to work with (especially if you're
boosting a range of frequencies).
2. Try to avoid massive amounts of boost or cut. If you're only trying to impart a flavor (like
sprinkling salt and pepper on a meal), then 6-8 dB of boost or cut should be all that you
need.
3. A wide bandwidth cut is equivalent to a boost at the frequencies surrounding the cut.
4. A quick way to figure out what's going on is to set the level of one band of the equalizer to
full boost (+18 dB), then switch to the frequency control and vary the frequency of that
band of the equalizer while listening to program material fed through the unit. This
usually makes quick work out of finding the region that you want to work on. Now reduce
the level setting to something tasteful.
To tailor your station's announce sound, begin with a general idea of the sound (voice
coloration) you want. Since you only have three general locations that you can equalize at,
you'll need to begin with the aspects of your sound that are most important.
Microphone choice is very important, since every microphone imparts its own equalization to
any sound that it hears. If you want a large, "ballsy" sound, you ought to think about single-D
microphones such as those made by AKG, Shure, Neumann, Sennheiser, and EV (like the

2-5
Rev 2.2, 10/31/94
RE38N/D or ND series) or a ribbon microphone such as the RCA 77DX. The built-in bass boost
caused by close talking a single-D microphone (proximity effect) can be tailored or tamed with
careful equalization, which also reduces room rumble at the same time. Last, since the
proximity effect increases with decreasing source-microphone distance, a skilled user can
substantially change their sound simply by moving in or out from the microphone.
If clarity is your goal, then a variable-D microphone such as the EV RE-20 or RE-18 or an
omnidirectional type such as the EV RE50 or AKG414 (with the pattern set to omni) is a good
choice as these types do not emphasize the bass frequencies when you close-talk them. On the
negative side, any room rumble present with the microphone will be boosted along with the
voice if you try to equalize at the lower frequencies.
Next, add or remove low frequencies in the 100-300 Hz range until you get a weight or fullness
that is pleasing. Next add midrange boost in the 2.5 kHz to 5 kHz range to add punch and
presence (experiment with the bandwidth control!), and finally add or remove frequencies in the
10000+ Hz range to get the sense of brilliance that you want.
It’s sometimes difficult to translate what you are hearing into the numbers that make
equalizers happy. Seeing the frequencies associated with a voice or instrument can be helpful
in deciding where equalization may be needed. The chart shown in Figure 2-1 shows the
relationships of many different instruments, and a piano keyboard along with the frequencies
involved.

2-6 Rev 2.2, 10/31/94
C
D
E
F
G
A
B
G
D
C
E
F
A
B
G
D
C
E
F
A
B
G
D
C
E
F
A
B
G
D
C
E
F
A
B
G
D
C
E
F
A
B
G
D
C
E
F
A
B
G
D
C
E
F
A
B
C
D
0000000111111122222223333333444444455555556666666777777788888889999999
A
F
E
G
B
A
C
F
E
D
G
B
BASS
BARITONE
TENOR
ALTO
SOPRANO
BASS VIOL
CELLO
VIOLA
VIOLIN
KETTLE DRUM
BASS TUBA
BASSOON
BASS CLARINET
TROMBONE
FRENCH HORN
TRUMPET
CLARINET
OBOE
FLUTE
PICCOLO
WIND
INSTRUMENTS
STRING
INSTRUMENTS
HUMAN
VOICE
BASS
TREBLE
16.35
18.35
20.60
21.83
24.50
27.50
30.87
32.70
36.71
41.20
43.65
49.00
55.00
61.74
65.41
73.42
82.41
87.31
98.00
110.00
123.47
130.81
146.83
164.81
174.61
196.00
220.00
246.94
261.63
293.66
329.63
349.43
392.00
440.00
493.88
523.25
587.33
659.26
698.46
783.99
880.00
987.77
1046.50
1174.70
1318.50
1396.90
1568.00
1760.00
1975.50
2093.00
2349.30
2637.00
2793.80
3136.00
3520.00
3951.10
4186.00
4698.60
5274.00
5587.60
6272.00
7040.00
7902.20
8372.00
9393.20
10548.00
11175.20
12544.00
14080.00
15804.40
Figure 2-1. Relationships of Musical instruments, Piano, and actual frequencies.

2-7
Rev 2.2, 10/31/94
Converting the descriptive adjectives that people use to describe the character of a voice into
numbers that make equalizers happy is a common problem. Figure 2-2 lists some commonly
used adjectives and their corresponding frequency ranges.
2.4.9 Peaking or Shelving?
At very narrow bandwidths (small number),
peaking equalizers exhibit a phenomenon known as "ringing." This quite aptly describes the
effect of the equalizer being sharply resonant at its center frequency, which makes it almost
oscillate.
In general, use the shelving curves to create overall color changes to the entire signal, and use
the peaking curves to modify specific regions of the signal. The peaking curves bring another
variable into play, "bandwidth" or "Q" as it is sometimes known. The bandwidth parameter
simply tells you how much of the region surrounding the center frequency will be affected.
Bandwidth and Q are inversely related; that is, a wide bandwidth (large number) corresponds
to a low Q (small number).
2.5 De-Essing
De-essing is the process of removing "S" sounds from speech or singing. The technique was
originally developed for motion picture dialogue recording when it was discovered that speech
Range Description (women)
100-250 Hz Fullness
250-400 Hz Bassiness, bigness
400-600 Hz Warmth
600-1 kHz Volume
2 kHz-4 kHz Clarity
3 kHz - 5 kHz Nasal, yell, presence
5 kHz-8 kHz Enunciation, intimacy
10 kHz up Air, mouth noises
Range Description (men)
75-200 Hz Balls, rumble, heaviness
200-300 Hz Bassiness, bigness
400-600 Hz Chesty
600-1 kHz Volume
2 kHz-4 kHz Clarity
3 kHz Nasal, yell, presence
5 kHz-8 kHz Enunciation, intimacy
10 kHz up Air, mouth noises
Figure 2-2. Descriptive adjectives used for voice ranges of men and women.
The 601s equalizer can operate in either
peaking or shelving mode. The two terms refer
to the overall shape of the equalizer's frequency
response curve. In Figure 2-3, you can see that
the peaking equalizer's effect is concentrated at
one frequency (the center frequency), with
progressively less effect above or below the
center frequency. The shelving equalizer (which
acts more or less like the tone controls on a
home stereo) affects frequencies above or below
its characteristic frequency (depending on
whether we're talking about a low-frequency
shelving equalizer or a high-frequency shelving
equalizer).
Shelving
E.Q. Peak/Dip
E.Q.
Rev-A
Figure 2-3. Shelving and peak/dip EQ curves.

2-8 Rev 2.2, 10/31/94
sounded more natural when the accentuation of sibilants ("s" sounds) was reduced. By sensing
and limiting certain frequencies, the de-esser is intended to provide more specific control over
some of the higher frequency vocal sounds that tend to become overemphasized.
Most sibilant vocal sounds like "s", "sh," and "t" are very difficult to reproduce electronically
because they contain a large percentage of very high frequency harmonics. Since these sounds
are so essential to the intelligibility of speech, they can't be simply removed with equalization.
In fact, to help maintain articulation, many sound engineers routinely boost the higher
frequencies of the vocal spectrum (3 kHz to 8 kHz), and/or use microphones with "presence
curves" (like the Neumann U-87 or AKG C-414). However certain individuals and even certain
languages contain overemphasized sibilants and any sort of high frequency boost only
exacerbates the problem.
2.6 Noise Reduction
Noise reduction is the process of removing the noise from a signal without (hopefully) affecting
the signal itself. There are two types of noise reduction: single ended (the 601), and double-
ended (like Dolby noise reduction2).
A double-ended system such as the Dolby System eliminates noise contributed between its
encode and decode processors. By necessity, this means that you must have access to the
signal before it has noise added to it, and afterwards. For tape recorders and their ilk, this is
perfect. Of course, if you feed a Dolby noise-reduced system a noisy signal, it will simply hand
it back to you, without any added noise of course, but with just as much noise as you gave it to
begin with (garbage in, garbage out or GIGO).
A single ended noise reduction system works on whatever signal you hand it. Single-ended
systems depend on noise masking by the signal. That is, when the signal is present, it tends to
mask the noise. So when the signal is quiet or absent, reduce the noise (by reducing the high-
frequency response), and when the signal is present, remove the high-frequency rolloff and
pray that the signal masks the noise.
If you're handed a noisy signal, then a single-ended noise reduction processor is your best
weapon against the noise. If you combine this with some careful equalization, you'll probably
end up with a signal that is more listenable.
2.7 Downward Expansion
Expansion is the process of increasing a signal's dynamic range, usually by increasing the
signal's level by a precise amount for every dB over a magic signal level (the "threshold").
Unfortunately, this requires infinite (or at least near infinite) headroom.
A simple, but entirely satisfactory solution is to reduce the signal's level for every dB below a
magic signal level (the "threshold"). This is called downward expansion. A similar and related
device is the signal gate. You can think of a signal gate as a special case of a downward
expander (or vice-versa if you must). Both devices reduce their output when their input signal
falls below threshold. The difference is the rate (not speed) at which they do it. The 601’s
downward expander output falls at an adjustable rate for every 1 dB below threshold of the
input signal. A gate's output falls by a nearly infinite amount for the slightest change, below
threshold, of the input signal. You can think of a gate as a downward expander taken to the
extreme, or you can think of a downward expander as a subtle example of a gate.
Gates are generally used to remove leakage (unwanted signals from nearby sources) from a
signal. Downward expanders are used to remove extraneous noise and to increase dynamic
range by making the softer parts softer.
Compressors or limiters (for the purposes of this discussion, a limiter is simply a high-ratio
compressor) are often used to reduce dynamic range by setting an upper limit on larger signals.
2Dolby is a trademark of Dolby Laboratories, San Francisco, CA, USA.